Liquid Jet Head Electrode Slope Design for Insulation Breakdown Prevention
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Solution Overview
Problem
Piezoelectric elements in ink jet type recording heads are prone to breakage due to external humidity, and existing solutions that cover the piezoelectric material layer with an upper electrode can lead to insulation breakdown between electrodes.
Innovation Solution
A liquid jet head design where the lower electrode has a narrower width than the pressure generation chamber, with the piezoelectric material layer covering the upper and end surfaces, and the upper electrode extending to cover the piezoelectric material layer, maintaining a sufficient distance to prevent insulation breakdown and moisture exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piezoelectric material layer is covered with the upper electrode to prevent breakage due to humidity, then the piezoelectric material layer can be protected from moisture, but the upper electrode and the lower electrode become very close to each other, causing insulation breakdown
Solution Approach 1:
The patent applies dimensional change by forming a slope surface on the piezoelectric material layer that transitions from the upper surface to the end surface. This slope surface creates additional spatial distance between the upper electrode and lower electrode in the vertical dimension, while the upper electrode still covers the piezoelectric material layer to prevent moisture ingress. The slope surface effectively uses the third dimension (height/depth) to resolve the contradiction between moisture protection and insulation prevention.
2Object-affected harmful factors
If the upper electrode covers the piezoelectric material layer to prevent moisture exposure, then the piezoelectric element durability is improved, but the distance between upper electrode and lower electrode becomes insufficient, leading to insulation breakdown
Solution Approach 1:
The slope surface on the piezoelectric material layer utilizes the vertical dimension to create sufficient clearance between the upper and lower electrodes. By sloping the piezoelectric material layer downward toward the outside, the end surface is positioned at a greater vertical distance from the lower electrode compared to a flat configuration, thereby preventing insulation breakdown while maintaining moisture protection.
3Reliability
If the lower electrode width is made smaller than the pressure generation chamber width, then the piezoelectric material layer can cover the lower electrode surfaces for protection, but the electrode structure becomes more complex
Solution Approach 1:
The patent applies local quality by making the lower electrode width smaller than the pressure generation chamber width only in the regions where the piezoelectric material layer needs to cover it for protection. The lower electrode maintains appropriate width in other regions to fulfill its electrical function. This localized dimension change allows the piezoelectric material layer to cover the lower electrode surfaces without requiring a complete redesign of the entire electrode structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the durability of the piezoelectric elements by preventing breakage from humidity and ensuring reliable insulation, thereby improving the overall durability of the liquid jet head.
Implementation Method 1
a piezoelectric element provided above one surface of the flow channel forming plate, each of the piezoelectric elements having a lower electrode, a piezoelectric material layer, and an upper electrode. Pressure is given into the pressure generation chambers by displacement of the piezoelectric elements
Data Source
AI summary
A lower electrode 60 in a region opposite each of pressure generation chambers 12 is formed to have a width smaller than the width of the corresponding pressure generation chamber 12, and an upper surface and an end surface of the lower electrode 60 in a region corresponding to each of the pressure generation chambers 12 is covered with a piezoelectric material layer 70. An end surface of the piezoelectric material layer 70 forms a slope surface sloping downward toward the outside, an upper surface and an end surface of the piezoelectric material layer 70 in the region opposite each of the pressure generation chambers 12 are covered with an upper electrode 80, and a distance D1 between the upper surface of the lower electrode 60 and the upper surface of the piezoelectric material layer 70 and a distance D2 between the end surface of the lower electrode 60 and the end surface of the piezoelectric material layer 70 satisfy the relationship D2≧D1.